A Garratt is a type of steam locomotive that is articulated into three parts.[citation needed] Its boiler is mounted on the centre frame, and two steam engines are mounted on separate frames, one on each end of the boiler. Articulation permits larger locomotives to negotiate curves and lighter rails that might restrict large rigid-framed locomotives. Many Garratt designs aimed to double the power of the largest conventional locomotives operating on their railways, thus reducing the need for multiple locomotives and crews.

In 1907 Beyer, Peacock & Co. submitted a proposal for a 2 ft (610 mm) gauge 0-4-0+0-4-0 Garratt to the New South Wales Government Railways, which was not proceeded with. The following year a design for a 2 ft gauge Mallet locomotive was submitted in reply to an enquiry from the Government of Tasmania. This was followed with a submission for a Garratt based on, but a little heavier than, the New South Wales proposal. This proposal was accepted, and two locomotives were built in 1909, which became the K class.[2] The K class had to cope with 99' radius curves and 1 in 25 gradients.[3]

Unlike in Garratt's patent, Tasmanian Railways insisted on a compound arrangement with cylinders facing inwards, in order to reduce the distances between both the main steam pipe and the high-pressure cylinders, and between the high-pressure and low-pressure cylinders. This made the locomotive unnecessarily complicated and placed the high-pressure cylinders directly underneath the cab, making it uncomfortably hot, especially in summer. The pattern was not repeated on later Garratt designs. Only one more Garratt locomotive, again built by Beyer, Peacock & Co. in 1927, was produced with compound propulsion for the Burma Railways.[4]

Early design and construction difficulties involved the steam-tight flexible connections between the boiler unit and the power units. These were solved by Beyer, Peacock's designers after studying a description of the spherical steam joints used on a Fairlie locomotive built for the Ffestiniog Railway followed by a visit to the FR to observe these locomotives at work.[5]

The third Garratt (another 0-4-0+0-4-0, like the first two) was built in 1910 for the Darjeeling Himalayan Railway, and given the class letter "D". As with many early Garratt classes, this engine's dimensions and power were designed to be roughly equivalent to those of two of the line's existing 0-4-0T engines, although in practice it achieved only a 65% increase in loading.[6]

The final Garratts to a Beyer-Peacock design were built in 1967–1968, eight 2 ft (610 mm) gauge South African Railways Class NG G16 locomotives. The order was placed with Beyer, Peacock and Company, but since the firm was in the process of closing down, it subcontracted the order to the Hunslet Engine Company. Hunslet's South African subsidiary, Hunslet-Taylor in Germiston, built these locomotives using boilers manufactured by their mother company.[1]

The 500 mm (193⁄4 in) gauge Southern Fuegian Railway (F.C.A.F.) in Argentina procured a new Garratt in 1994. Based on Livio Dante Porta's work, it included larger cross section tubing, insulation of the boiler and an improved front end. This vastly improved the economy of this modern steam engine and more than doubled train length. Accordingly, a second Garratt for this railway was built to similar specifications, but with superheating added, in the workshops of Girdlestone Rail in Port Shepstone, South Africa. It was shipped to Argentina in 2006 and entered service in October of that year.[7]

The Garratt was most widely used in Africa,[1] with large numbers in South Africa, Rhodesia (now Zimbabwe) and Algeria and smaller numbers in Angola, Congo, Ivory Coast, Kenya, Libya, Madagascar, Mozambique, Senegal, Sierra Leone, Sudan, Uganda, and Zaïre.

In Algeria 29 4-6-2+2-6-4 Garratts, constructed between 1936 and 1941 by the Société Franco-Belge de Materiel de Chemins de Fer at Raismes in Northern France, operated until the Algerian independence war caused their withdrawal in 1951. This class, designated 231-132BT, was streamlined and featured Cossart motion gear, mechanical stokers and 1.8 m (5 ft 11 in) driving wheels, the largest of any Garrett class. On a test in France, one of these achieved a speed of 132 kilometres per hour (82 mph)—a record for any Garratt class (and indeed any articulated class).[11]

The largest user was the 3 ft 6 in (1,067 mm) gauge Caminho de Ferro de Benguela. Forty-eight were purchased from Beyer, Peacock between 1926 and 1956. They came in four batches, class 10A (301–306); class 10B (311–324) in 1930; class 10C (331–348) in 1954; and class 10D (361–370).

The second-largest user was the Caminhos de Ferro de Luanda, who bought six 4-8-2+2-8-4 locomotives (501–506) from Beyer, Peacock in 1949, and six more (551–556) from Krupp of Germany in 1954.

The largest and most powerful steam locomotives to run on the metre gauge were the East African Railways (EAR) 59 class Garratts, each of them a 4-8-2+2-8-4 locomotive that delivered a tractive effort of 83,350 pounds-force (370.76 kilonewtons). These thirty-four oil-fired East African Garratts had large 70 square feet (6.5 square metres) grates and were among the largest and most powerful steam locomotives in the world, remaining in regular service until 1980. Two survive, no. 5918 and 5930. Both have worked since 1980 on tourist excursion trains but are now both out of service and belong to the Nairobi Railway Museum.[12]

The Garratts that ran on the East African Railways, the earlier ones having been inherited from the Kenya Uganda Railways (KUR) or the Tanganyika Railways (TR), were:

All were built by Beyer-Peacock in Manchester, England, except the 52 class which was built by North British Locomotive Company in Glasgow and some of the 60 class which were built by Société Franco-Belge in France. All were of the 4-8-2+2-8-4 wheel arrangement, except the 57 and 58 classes which were 4-8-4+4-8-4.

Rhodesia imported 246 Garratts of four different wheel arrangements: 2-6-2+2-6-2s of the 13th, 14th and 14A classes; 4-6-4+4-6-4s of the 15th class, 2-8-2+2-8-2s of the 16th, 16A, and 18th classes; and 4-8-2+2-8-4s of the 20th and 20A classes. Many went to Zambia Railways in 1967 when Rhodesia Railways surrendered the lines in Zambia to its government. Zimbabwe's economic and political situation has extended the life of its Garratts. Five Garratts, including some from the Zimbabwe National Railway Museum, were returned to service in 2004–05 to haul commuter trains. They also perform shunting duties around the city of Bulawayo to this day (December 2011).[13][14]

The most powerful of all Garratts irrespective of gauge were the South African Railways' eight GL class locomotives of 1929–30, which delivered 89,130 lbf (396.47 kN) of tractive effort. However, they were all out of service by the late 1960s.[15] There was also a proposal for a quadruplex super Garratt locomotive with a 2-6-6-2+2-6-6-2 wheel arrangement for South African Railways, but this was never built.[16]

Burma had 43 metre gauge Garratts. Five B class 2-8-0+0-8-2 Garratts went to the Burma Railway Company between 1924 and 1927, with seven more built by Krupp of Germany in 1929.[18] They were followed by 31 locomotives transferred from India for War Department service: ten 2-8-0+0-8-2 locomotives, class GB (ex-Indian class MWGL); twelve 2-8-2+2-8-2 locomotives of class GC (ex-Indian class MWGH); and nine 4-8-2+2-8-4 locomotives of class GD (ex-Indian class MWGX).[19][20][21] A class of four 4-8-2+2-8-4 locomotives, the GE class, was built for Burma Railways in 1949,[21] but was diverted to the Assam Railway in India.[22]

India had 83 Garratts. One 5 ft 6 in (1,676 mm) gauge 2-6-2+2-6-2 was built for the Indian State in 1925.[21] The 5 ft 6 in gauge Bengal Nagpur Railway had 32 Garratts: a pair of HSG class 2-8-0+0-8-2 locomotives built in 1925; 16 N class and 10 NM class 4-8-0+0-8-4 locomotives built in 1930–31 and four P class 4-8-2+2-8-4 locomotives built in 1939.[21][24]

The metre gauge Assam-Bengal Railway had six T class 2-6-2+2-6-2 locomotives built in 1927. They later became the GT class on the Bengal Assam Railway. Three types of Garratt were supplied for war service on the BAR: ten MWGL class 2-8-0+0-8-2 locomotives; twelve MWGH 2-8-2+2-8-2 locomotives; and 18 MWGX class 4-8-2+2-8-4 War Department standard light Garratts. Of these, only nine MWGX stayed in India, with the remainder transferred to Burma.[19][21] After the war, the four Burma Railways GE class 4-8-2+2-8-4s were diverted to the Assam Railway.[citation needed]

Beyer, Peacock built three 4-6-2+2-6-4 NZR G class locomotives in 1928, which were too powerful for the system and had complicated valve mechanisms. Unusually, these engines had three cylinders (24×16.5 in) each, on two sets of engine frames, thus creating a six-cylinder Garratt; they were the second and final Garratts to employ this arrangement, the other being the aforementioned LNER U1. They entered service in 1929. Walschaerts valve gear operated the outside cylinders with the inner third cylinder linked by a Gresley conjugated valve gear. Photos verify the coal bunker was carried on an extension to the boiler frame rather than on the rear engine frame, as with most Garratts. The engines delivered 51,580 lbf (229.44 kN) of tractive effort, which was too powerful for the drawbars on the rolling stock. After a few years they were rebuilt as six Pacifics, also unsuccessful, but which saw nearly twenty years of service.[26]

New South Wales Government Railways introduced the 4-8-4+4-8-4AD60 Garratt in 1952, built by Beyer, Peacock. The AD60 weighed 265 tonnes, with a 16-tonne axle loading. As delivered, it developed a tractive effort of 60,000 lbf (270 kN)), not as powerful as the South African Railways GMA/M 4-8-2+2-8-4 Garratts of 1954, which developed a tractive effort of 60,700 lbf (270 kN).[15] Following modifications in 1958 to thirty AD60s, their tractive effort was increased to 63,016 lbf (280.31 kN). These locomotives remained in service until the early 1970s with a replacement "6042" (The original was scrapped in 1968) the last withdrawn in February 1973.[27] Oberg wrote he witnessed an AD60 clear a dead 1220-tonne double-headed diesel freight (total weight 1450 tonnes) from a 1 in 55 grade without wheel slip.[28]

Following the success of the K class Garratts on the North East Dundas Tramway, the Tasmanian Government Railways imported Beyer, Peacock Garratts for their main lines, in particular the 4-4-2+2-4-4M class for express passenger work. These were the only eight-cylinder Garratts.[30] The M1 achieved a world speed record of 55 miles per hour (89 km/h) on 30 November 1912. Their 5-foot (1.5 m) diameter driving wheels were at the time the largest on any narrow-gauge locomotive in Australia.[31] Their eight cylinders proved a nightmare to maintain, and after several fatal and disastrous derailments in the late 1920s, mainly due to inadequate trackwork, they were withdrawn and scrapped.

Garratts were mainly employed in Great Britain, Russia and Spain, where some five railway companies employed seven classes. These included the 1931 order for Central of Aragon Railway for six Double Pacific Garratts for fast passenger service. In addition a Dutch and a Belgian tramway also operated one or more engines based on and built to the Garratt design.

In 1931 the Dutch Limburgsche Tramweg Maatschappij (LTM) 'Limburg tramway company' ordered a single standard gauge Garratt, numbered LTM 51, from Henschel (Germany) with builder's number 22063. This design was slightly different in that the coal bunker was located on the boiler frame and both machines only holding the watertanks. More importantly, it was the only Garratt with inside cylinders. The wheel arrangement was C+C (0-6-0+0-6-0). Due to abandonment of the line in 1938 the loc was sold to a metal merchant, who in turn sold it to an engineers' bureau, that sold it in 1941 to Germany. Further whereabouts of this machine are unknown, but it is presumed scrapped.

Spain had a varied collection of Garratts from most builders; Beyer, Peacock themselves only building a pair of 3 ft 6 in (1,067 mm) 2-6-2+2-6-2s for Rio Tinto in 1929. The first Garretts in Spain however were four metre gauge 2-6-2+2-6-2s built for the Ferrocarriles Catalanes in 1922 by Sociéte Anonyme St. Leonard of Liége, Belgium. Four more followed in 1925. Also on the metre gauge, the Ferrocarril de la Robla bought two pairs of 2-6-2+2-6-2s, the first from Hanomag of Germany in 1929, the second from Babcock and Wilcox of Bilbao in 1931. The Compania Minera de Sierra Minera also bought a pair of metre gauge 2-6-2+2-6-2s in 1930.

On the broad gauge, the Central of Aragon Railway bought six 2-8-2+2-8-2s from Babcock and Wilcox and six 4-6-2+2-6-4s from Euskalduna of Bilbao, both in 1931. The last Garratts supplied to Spain were ten 2-8-2+2-8-2s for RENFE by Babcock and Wilcox in 1960.

Beyer, Peacock constructed the largest steam locomotive built in Europe, a 4-8-2+2-8-4 for the USSR, works order number 1176 in 1932. The locomotive had the Russian classification Ya.01 (Я.01). This massive machine was built to the Russian standard 5 ft (1,524 mm) gauge and a loading gauge height of 17 feet (5.2 m). It underwent extensive testing and proved to be very able to operate in extremely low temperatures, due to adequate protection of the external plumbing between boiler and engine units. This may have been the lowest temperature operation of a Garratt type. The locomotive was used for a number of years for coal traffic in the Donbass region, but was never replicated. This decision appears to be a combination of unfamiliar maintenance processes and politics.[32][33][34] The Russians later experimented with Mallet locomotives, the P342-6-6-2 and the P382-8-8-4.[citation needed]

The British-owned 5 ft 6 in (1,676 mm) gauge Buenos Aires Great Southern Railway operated twelve Garratt 4-8-2+2-8-4 oil-fired locomotives, numbers 4851–4862, built by Beyer, Peacock in 1929. They were used on the Bahía Blanca North Western section, particularly on the Toay line), on the main Bahía Blanca North Western line to General Pico, and between Tres Arroyos and Bahía Blanca. They were withdrawn in the 1950s due to the rapid decline in freight traffic caused by the increasing competition from road transport.[35] The F.C.A.F in Ushuaia uses two 500 mm (193⁄4 in) gauge Garratts to haul tourists into a National Park.

Other British-owned railway companies in Argentina operated Garratt locomotives built by Beyer, Peacock:

Works drawings of K1, showing how the boiler and firebox are not inhibited by the running gear

The principal benefit of the Garratt design is that the boiler and firebox unit are slung between the two engine units. This frees the boiler and firebox from the size constraints imposed where they are placed over the frames and running gear, as in conventional designs and other articulated designs such as Mallets. Garratts can have a boiler with a greater diameter, which increases heating area and aids the production of steam. The boiler can also be shorter than other designs with the same heating area. In some loco designs, the boiler is so long almost no heating of the water occurs at the smokebox end of the boiler. A larger firebox promotes more efficient combustion of fuel and also increases the heat available to the boiler.[citation needed]

Garratts enjoy an advantage over the Mallet system, because of the geometry of the design. When swinging around curves the boiler and cab unit move inward like a bowstring in the bow of a curve and this reduces the centrifugal force that would overturn a normal locomotive and which in turn permits faster running. The Mallet's forward articulated unit tends to throw out as the loco rounds curves.[12] While most Garratts were designed for freight or mixed traffic, there were a number of passenger Garratt classes. A Garratt holds the world speed record for an articulated locomotive.[citation needed]

Garratts have several advantages when used on light and narrow gauge railways. They are tank locomotives and can easily be run tender-first, thus eliminating the need for expensive turntables or wyes. They do not need to be run through to terminals, increasing operational flexibility. Because the engine units are separated by the boiler unit, the weight of the locomotive is split over the two units, and they can run over bridges or line sections that might not be able to support conventional or Mallet locomotives of similar weight.[citation needed]

While at the end of the steam locomotive era most conventional steam locomotives had reached their maximum in "critical dimensions", the Garratt still had some way to go, with larger driving wheels, larger boilers and greater output still achievable.[12]

The major disadvantage of a Garratt (shared with all tank engines) is that the adhesive weight decreases as the water is used from the front tank and coal from the rear bunker. As the weight on the wheels decreases slipping occurs. To reduce wheelslip, a wagon containing water was attached behind the Garratt, and this practice also permitted the engine to operate over longer distances.[where?][citation needed] The weight of the water in the locomotive's tank and weight of coal in the bunker (necessary for the factor of adhesion) was predicted in advance, and this problem was not normally an operational issue.[citation needed]

The Garratt was, obviously, not alone in the field of articulated locomotives. Aside from the well-known Fairlie and Meyer types, the Garratt had contemporary and similarly-designed competition in the form of the Union-Garratt, Modified Fairlie and Golwé. Of these, the closest was the Union-Garratt, a type originally conceived owing to the perceived necessity for a rigid connection between a bunker or tender and a firebox fed by a mechanical stoker. Though it could be argued that the NZR G class locomotives were Union-Garratts (having their bunkers mounted on the boiler frames, rather than on the hind engine unit), a more concrete example can be seen in the two South African Railways Union Garratts of classes GH and U.

The Union-Garratt did not enjoy the success of the standard Garratt. It was soon evident that mechanical stokers could function perfectly across the connection between a Garratt's boiler and engine unit, making the rationale for the Union-Garratt obsolete. The Union-Garratts' extended boiler frames and the position of the bunker and hind water tank upon those frames meant that they suffered from many of the problems which beset the Mallet design; the SAR U and GH classes had much heavier axle-loadings than Garratts of comparable size, weight and power, and the movement of water at the extreme ends of the long main frames generated high wear on the hind pivot between the boiler and engine unit. The Union-Garratt, like the Golwe and Modified Fairlie, was not perpetuated on anything like the scale of the Garratt, and no known examples survive.

Seventy Garratts were constructed by Beyer, Peacock for the War Department, to three standard designs. A 2-8-2+2-8-2 based on the South African Railways GE class was constructed on 3 ft 6 in (1,067 mm) gauge for West Africa and Rhodesia, while a heavier class of 4-8-2+2-8-4 was constructed for East African Railways. A lighter metre-gauge 4-8-2+2-8-4 was constructed for India, Burma, and East Africa. This design was particularly successful, and was the basis for several post-war classes.[1]

The Australian Standard Garratt (ASG) was constructed for Australian 3 ft 6 in gauge railways. It was a 4-8-2+2-8-4 locomotive, designed and constructed in Australia in 1943, during the crisis days of World War II immediately following the bombing of Darwin in 1942.[39] The class had several design problems, and encountered resistance from unions, and most were withdrawn at the end of the war.[1]

Around 250 Garratts exist today. While many are stored or dumped in various stages of disrepair, more than 100 are preserved in museum collections or on heritage railways. Operating Garratt locomotives can be found in Europe, Africa, India and Australia.[40] In Spain, a 2-8-2+2-8-2 number 282F-0421, nicknamed "Garrafeta", occasionally runs in the Lleida area. An enormous 4-6-2+2-6-4, number 462F-0401, is under restoration. Both locomotives are managed by ARMF, a non-profit organisation which also holds the only main line repair workshop for historical railway vehicles on broad gauge network.[41]

A single Hanomag-built narrow gauge example exists in the USA located in Texas.

The first Garratt locomotive, the K class of the North-East Dundas Tramway, has been preserved. After the line closed in 1929 the locomotives were put up for sale. K1 was purchased by Beyer, Peacock in 1947 for their museum. The preserved loco has parts from both original engines, including the boiler from K2. When Beyer, Peacock ceased trading, the locomotive was sold to the Ffestiniog Railway, who initially proposed to cut it down to meet their loading gauge. For a number of years it was on loan to the National Railway Museum and was exhibited in York. In 1995 it was removed from York to commence restoration in Birmingham. It was returned to Wales in 2000 where restoration was continued at the Ffestiniog Railway workshops at Boston Lodge. It was fitted with a new boiler and restored to full running order on the Welsh Highland Railway in September 2006. The Welsh Highland Railway owns several former South African SAR NGG 16 Class Garratts, and operates both the first and last Garratts constructed by Beyer, Peacock.[42]

In Kenya, East African Railways 59 class 5918 was maintained in operating condition. Likewise in Zimbabwe20th class 730 and 740 were held in operating condition. They have not run since 2004 when 730 was briefly used on Bulawayo commuter services. None are likely to operate again without external funding for major repairs as the only work available for them are excursion trains for foreign tourists and rail enthusiasts.

In December 2007, Zimbabwe class 14A Garratt number 509, overhauled in Bulawayo was offloaded in New Zealand for operational preservation by the Mainline Steam trust.[43] In early 2011 Zimbabwe 15th class 398 was also delivered to New Zealand for restoration to operating condition by Steam Inc.

As of February 2011 there are only two places in the world where one can with reasonable confidence view a Beyer-Garratt in daily operating service. Bulawayo/Hwange, Zimbabwe and Ushuaia, Argentina whilst Dinas in North Wales offers the sight of daily operation for about 10 months of the year.

Manning, Peter (2009). The Anatomy of a Garratt: A detailed look at the design and construction of K1. The original Garratt locomotive built for the Tasmanian Government Railways - A century ago. Coromandel Valley, SA, Australia: Peter Manning Design & Drafting. ISBN9780980621228.